Fix for bug#17826 'type_decimal' fails with ps-protocol

 removed unnecessary calculation of cache value 
 otherwise Join::preapre tries to calculate 
 undefined values(filed values)

mysql-test/r/type_decimal.result

@@ -772,3 +772,10 @@ productid	zlevelprice
 003trans	39.98
 004trans	31.18
 drop table t1, t2;
+create table t1 (f1 decimal(5));
+insert into t1 values (40);
+flush tables;
+select f1 from t1 where f1 in (select f1 from t1);
+f1
+40
+drop table t1;

mysql-test/t/type_decimal.test

@@ -377,3 +377,11 @@ insert INTO t2 SELECT * FROM t1;
 select * from t2; 
 drop table t1, t2;
 
+#
+# Bug #17826 'type_decimal' fails with ps-protocol
+#
+create table t1 (f1 decimal(5));
+insert into t1 values (40);
+flush tables;
+select f1 from t1 where f1 in (select f1 from t1);
+drop table t1;

sql/item_cmpfunc.cc

@@ -698,12 +698,6 @@ bool Item_in_optimizer::fix_left(THD *thd, Item **ref)
     return 1;
 
   cache->setup(args[0]);
-  /*
-    If it is preparation PS only then we do not know values of parameters =>
-    cant't get there values and do not need that values.
-  */
-  if (!thd->stmt_arena->is_stmt_prepare())
-    cache->store(args[0]);
   if (cache->cols() == 1)
   {
     if ((used_tables_cache= args[0]->used_tables()))